DK165968B

DK165968B - PROCEDURE FOR REMOVAL OF POLLUTANTS CONTAINED IN POWDER GASES

Info

Publication number: DK165968B
Application number: DK520785A
Authority: DK
Inventors: Jean Remillieux
Original assignee: Air Ind Environnement
Priority date: 1984-11-12
Filing date: 1985-11-12
Publication date: 1993-02-22
Also published as: PT81471A; HUT46560A; PT81471B; EP0182706B1; HU202424B; FI83042C; DK165968C; FI854447A; DK520785D0; AU4982385A; EP0182706A1; DE3569480D1; ATE42218T1; JPS61181522A; ZA858670B; FR2572951A1; DK520785A; ES548778A0; ES8702799A1; FI854447A0

Abstract

1. Semi-dry process for eliminating acid pollutants contained in fumes, in particular sulphurous anhydride, by a basic pulverulent treatment product of the type in which the said fumes are brought into close contact with the said product, in order that the latter absorbs the pollutants contained in the fumes by chemical reaction after which separation takes place between the gases treated and the product used in the treatment, the purified gases then being capable of being discharged into the atmosphere, characterised in that a quantity of water comprised between about 5 and 15% of the weight of the dry product is added to the dry product, i.e. a quantity of water small enough to keep the product in powder form, before suspending it in a rising stream of the said fumes, carried out in a reaction and drying column.

Description

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iin

Opfindelsen angår en fremgangsmåde til halvtør fjernelse af forurenende stoffer, især svovldioxid, indeholdt i røggasser, ved behandling med et basisk, pul verformigt materiale af kalktypen, ved hvilken røggasserne ved en opadgående strøm af 5 røggasserne i en reaktions- og tørringskolonne bringes i intim kontakt med materialet således, at det sidstnævnte ved kemisk reaktion kan absorbere de forurenende stoffer, især syrer, der er indeholdt i røggasserne, hvorefter man udfører en adskillelse af den behandlede gas og materialet, der har været an-10 vendt til behandlingen, og hvorefter den rensede gas kan ledes ud til atmosfæren.The invention relates to a method for semi-dry removal of pollutants, especially sulfur dioxide, contained in flue gases, by treatment with a basic, lime-type powdery material in which the flue gases are brought into intimate contact with an upward flow of the flue gases in a reaction and drying column. with the material so that the latter can absorb, by chemical reaction, the pollutants, especially acids contained in the flue gases, after which a separation of the treated gas and the material used for the treatment is carried out and then purified gas can be discharged into the atmosphere.

De omhandlede røggasser kan især udledes fra indsutrielle kedler til forbrænding af svovlholdigt kul, som f.eks. Gar-15 danne-kul, som ved forbrænding uden behandling giver gas med en S02~ koncentrat i on på ca. 4000 ppm. Det siger sig selv, at det er hensigtsmæssigt at behandle sådanne gasser, inden de slippes ud til atmosfæren.The flue gases in question can in particular be emitted from insulating boilers to the combustion of sulfur-containing coal, such as for example. Gar-15 forming coal, which, when incinerated without combustion, produces gas with a SO 2 concentrate in on of approx. 4000 ppm. It goes without saying that it is appropriate to treat such gases before they are released into the atmosphere.

20 øen intime kontakt mellem røggasserne og det basiske, pulver-formige materiale, især kalk, kan opnås i et fluidiseret leje, opnået ud fra partiklerne af dette materiale, hvilket leje herefter gennemstrømmes af røggasserne, der skal behandles, men de type fremgangsmåde har den ulempe, at den nødvendiggør 25 en større opholdstid, og den har derfor begrænset kapacitet.The intimate contact between the flue gases and the basic powdery material, especially lime, can be obtained in a fluidized bed obtained from the particles of this material, which bed is then flowed through the flue gases to be treated, but the type of method has the disadvantage that it necessitates a greater residence time and therefore has limited capacity.

Ved en anden fremgangsmåde anvender man forstøvere for det nævnte pulverformige materiale i vandig suspension, hvilke forstøvere virker i reaktionstårne, men denne fremgangsmåde 30 nødvendiggør en betydelig fordampning af vand, hvilket endvidere medfører en betydelig afkøling af gassen, og at de nødvendige anlæg er dyre og pladskrævende.In another method, atomizers for the said powdery material are used in aqueous suspension which operate in reaction towers, but this method 30 requires a considerable evaporation of water, which also results in a considerable cooling of the gas, and that the necessary plants are expensive and bulky.

Europæisk patentskrift nr. 0 022 667 angår en fremgangsmåde 35 til fremstilling af et neutraliserende middel til sure røggaskomponenter. Hertil opløses brændt kalk med et overskud af vand, og den resulterende suspension tørres til et pulver, somEuropean Patent Specification No. 0 022 667 relates to a process 35 for producing a neutralizing agent for acidic flue gas components. To this end, burnt lime with an excess of water and dissolve the resulting suspension to a powder which

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2 spredes i en gasstrøm. Fugtighedsindholdet er meget højt (op til 50%) og indebærer, at røggasserne skal have en meget høj temperatur for at være i stand til at bringe alt vand til at fordampe. Som det fremgår af skriftets spalte 4, linie 10-14, 5 er det vanskeligt at sprede pulveret i gassen. Derudover indebærer tørringen og spredningen af pulveret den ulempe, at rensningsprocessen totalt set i modsætning til, hvad der er tilfældet med fremgangsmåden ifølge den foreliggende opfindelse, er meget energikrævende.2 is dispersed in a gas stream. The moisture content is very high (up to 50%) and implies that the flue gases must have a very high temperature to be able to bring all the water to evaporate. As can be seen from column 4 of the script, lines 10-14, 5 it is difficult to disperse the powder into the gas. In addition, the drying and spreading of the powder implies the disadvantage that the purification process as a whole, contrary to the process of the present invention, is very energy intensive.

1010

Det tilsigtes med opfindelsen at overvinde disse ulemper ved de kendte fremgangsmåder, og dette opnås ved en fremgangsmåde, som defineret ovenfor, og som er ejendommelig ved, at det tørre pulverformige materiale tilsættes en vandmængde på ca.It is an object of the invention to overcome these drawbacks of the known processes, and this is achieved by a method as defined above, which is characterized in that the dry powdered material is added to a quantity of water of approx.

15 10 vægt% af det tørre materiale umiddelbart inden det indføres i reaktions- og tørringskolonnen.15% by weight of the dry material immediately before it is introduced into the reaction and drying column.

Herved opnås en fremgangsmåde, ved hvilken sure bestanddele af en røggas af en hvilken som helst type fjernes i en forholds-20 vis høj grad under brug af forholdsvis lidt energi og forholdsvis lidt vand. Dette skyldes især, at den tilsatte forholdsvis lille vandmængde befugter det pulverformede materiale, således at dets enkelte korn brydes op, og der herved let sker en fornyelse af de overflader, der går i direkte kon-25 takt med det reaktive materiale i røggasserne. Hertil kræver det kun en vandmængde på ca. 7-12 vægt%. Vandet tilsættes ved enkel sammenblanding uden, at der tilstræbes nogen kemisk gendannelse af et hydroxid. Den forholdsvis lille vandmængde lader sig let bringe til at fordampe, uden at røggassens tem-30 peratur påvirkes i væsentlig grad, hvorfor røggassens temperatur ikke behøver at være særlig høj, (100 - 200 eC).This provides a method by which acidic constituents of a flue gas of any type are removed to a relatively high degree using relatively little energy and relatively little water. This is mainly due to the fact that the relatively small amount of water moistens the powdered material so that its single grains are broken up, thereby easily replenishing the surfaces which are in direct contact with the reactive material in the flue gases. For this, it only requires a volume of water of approx. 7-12% by weight. The water is added by simple mixing without any chemical recovery of a hydroxide. The relatively small amount of water can easily be evaporated without significantly affecting the temperature of the flue gas, so the temperature of the flue gas need not be very high (100 - 200 eC).

Disse kolonner er allerede kendte til visse anvendelser. Der er tale om vertikale kolonner med stor højde, gennemstrømmet af 35 en hurtigt opadgående strøm af røggasserne, der skal behandles. Det reaktive, pul verformige materiale bringes i suspension i bunden af kolonnen, idet det tilføres og fordeles ned-These columns are already known for certain applications. These are high-altitude vertical columns, flowed by a rapid upward flow of the flue gases to be treated. The reactive powdery material is suspended at the bottom of the column as it is fed and distributed.

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3 strøms i forhold til en konvergent- divergent suspenderingsindsnævring.3 in relation to a convergent-divergent suspension constriction.

Det, at man ifølge opfindelen tilfører vandet til det basiske 5 pulverformige materiale, inden det bringes i suspension i kolonnen, muliggør, at man kan sætte reaktionerne mellem dette materiale og de sure røggasser igang under deres fælles opstigning i kolonnen, uden for stor afkøling af røggasserne, hvilket ville ske, hvis man indførte en vandig suspension af 10 reaktanten over den nævnte konvergente- divergente indsnævring. Idet vandmængden i forhold til reagenset i det sidste tilfælde er betydelig, vil afkølingen ligeledes værre for stor, når man tager røggassernes temperatur i betragtning (ca. 150eC ved afgangen fra en kedel).The addition of the water to the basic powdery material according to the invention before being suspended in the column enables the reactions between this material and the acidic flue gases to be initiated during their common rise in the column, without excessive cooling of the the flue gases, which would happen if an aqueous suspension of the reactant were introduced over said convergent divergent constriction. As the amount of water relative to the reagent in the latter case is considerable, the cooling will also be too great when considering the temperature of the flue gases (about 150 ° C at the exit of a boiler).

1515

Derimod kan man ved opfindelsen nøjes med at anvende en relativt lille mængde vand, på ca. 10 vægt% af materialet anvendt til behandlingen, uanset om det drejer sig om et friskt behandlingsmateriale eller en blanding med tilbageført mate-20 riale, dvs. materiale, som allerede har været anvendt til behandl ingen.On the other hand, it is sufficient for the invention to use a relatively small amount of water, of approx. 10% by weight of the material used for the treatment, whether it is a fresh treatment material or a mixture of recycled material, ie. material that has already been used for processing.

Hed en sådan mængde er reaktionen mellem kalken og svovldioxidet indeholdt i røggassen tilstrækkelig, medens afkølingen 25 af gassen er relativ lille, kun ca. 25°C. Endvidere er man langt fra mætning af røggassen med vand, hvorved undgås enhver risiko for kondensation i kolonnen. Vandet tilføres kun på det sted, hvor det skal anvendes.In such an amount, the reaction between the lime and the sulfur dioxide contained in the flue gas is sufficient, while the cooling of the gas is relatively small, only approx. 25 ° C. Furthermore, one is far from saturating the flue gas with water, thereby avoiding any risk of condensation in the column. The water is supplied only at the place where it is to be used.

30 Ved tilbageføring af kalk, hvilket er kendt, som allerede har været anvendt til behandlingen, til reaktionskolonnens bund, muliggøres opnåelse af en højere udnyttelsesgrad af kalken, ca. 80% med en afsvovlingsgrad, som kan nå op på mindst 90%.By returning lime, which is already known to the treatment, to the bottom of the reaction column, it is possible to obtain a higher utilization of the lime, approx. 80% with a degree of desulfurization, which can reach at least 90%.

35 Når støvet, indeholdt i røggasserne, er basisk, som det er tilfældet, når man brænder Gardanne-kul, muliggøres der desuden ved tilbageføring af støvet samtidig med det pulverfor-In addition, when the dust contained in the flue gases is basic, as is the case when burning Gardanne coal, it is possible to return the dust at the same time as the powder form.

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4 mige materiale, der allerede har været anvendt til behandlingen, opnåelse af en væsentlig besparelse af det friskt tilførte materiale, i dette tilfælde kalk. For en gas med en temperatur på 150°C og indeholdende 4000 ppm SO2, kan mængden af 5 tilført kalk f.eks. være 10-20 g/Nm3, mængden af tilbageført kalk og aske ca. 80 g/Nm3 og mængden af tilført vand 10 g/Nm3, hvilket medfører en temperatur af gassen efter separationen på ca. 125eC.4 material which has already been used in the treatment, obtaining a considerable saving of the freshly applied material, in this case lime. For a gas having a temperature of 150 ° C and containing 4000 ppm SO 2, the amount of lime added can be e.g. be 10-20 g / Nm3, the amount of lime and ash returned approx. 80 g / Nm3 and the amount of water added 10 g / Nm3, which causes a temperature of the gas after the separation of approx. 125eC.

10 Et anlæg, som kan anvendes til udøvelse af fremgangsmåden ifølge opfindelsen, beskrives herefter ved hjælp af et på ingen måde begrænsende eksempel med henvisning til tegningen.A plant which can be used for carrying out the method according to the invention is described hereinafter by means of an in no way limiting example with reference to the drawing.

I anlægget er reaktions- og tørringskolonnen, der i det væ-15 sentlige er vertikal, betegnet 1, og den har et konvergent-divergent stykke 2-3 forneden, og det pulverformige materiale, der anvendes ved behandlingen, indføres i kolonnen ved indsnævringen 4 i det konvergent- divergente stykke. Røggasserne, der skal behandles og f.eks. kommer fra en kedel til forbræn-20 ding af svovlholdigt kul, indføres forneden i kolonnen 1 via en tilførselsledning 5. Materialet, der anvendes til behandlingen, f.eks. pulverformigt kalk, indføres i kolonnen via en ledning 6, et lagerreservoir 7 og en tragt 8, fra hvis bund den udtages ved hjælp af en doseringssnegl 9. Inden indførslen 25 til indsnævringen 4 af det konvergent-divergente stykke af kolonnen, befugtes kalken i et anlæg 10, som forsynes med vand i en bestemt mængde via en tilførselsledning 11. Som angivet ovenfor er forholdet mellem mængderne af vand og kalk ca. 10 vægt% vand på basis af kalkens vægt, svarende til ca. 10 g 30 vand pr. Nm3 røggas ved 150°C og et S02-indhold på ca. 4000 ppm, under forudsætning af, at den befugtede kalk i princippet udgøres af dels ren kalk, der tilføres fra reservoiret 7, og dels tilbageført kalk i en samlet mængde på ca. 100 g/Nm3 røggas, idet det sidstnævnte tilføres til anlægget 10 via en 35 tilbageføringsledning 12. Ved en tilført mængde kalk på 10-20 g/Nm3 røggas, kan mængden af recirkuleret kalk (i blanding med aske) være ca. 80 g/Nm3. Denne foranstaltning muliggør såledesIn the plant, the reaction and drying column, which is substantially vertical, is designated 1 and has a convergent-divergent section 2-3 below, and the powdered material used in the treatment is introduced into the column by the narrowing 4 in the convergent-divergent piece. The flue gases to be treated and e.g. coming from a boiler for combustion of sulfur-containing coal, is introduced at the bottom of column 1 via a supply line 5. The material used for the treatment, e.g. powdered lime, is introduced into the column via a conduit 6, a storage reservoir 7 and a hopper 8 from whose bottom it is taken out by a metering screw 9. Prior to insertion 25 into the constriction 4 of the convergent-divergent piece of the column, the lime is wetted in a system 10, which is supplied with water in a specified amount via a supply line 11. As indicated above, the ratio of the amounts of water to lime is approx. 10% by weight of water based on the weight of the lime, corresponding to approx. 10 g 30 water per Nm3 flue gas at 150 ° C and a SO 2 content of approx. 4000 ppm, provided that the moistened lime is in principle made up of clean lime supplied from the reservoir 7 and partly reclaimed lime in a total amount of approx. 100 g / Nm3 of flue gas, the latter being supplied to the plant 10 via a return line 12. At an added amount of lime of 10-20 g / Nm3 of flue gas, the amount of recycled lime (in admixture with ash) may be approx. 80 g / Nm3. This measure thus enables

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5 besparelse af kalken tilført via ledningen 6, og sørger for at denne kalk udnyttes maksimalt til absorption af svovldioxid, indeholdt i røggasserne.5 saves the lime supplied via the conduit 6, and ensures that this lime is maximally utilized for the absorption of sulfur dioxide contained in the flue gases.

5 For at kalken kan fordeles på fuldstændig homogen måde i reaktionskolonnen, er en spreder 10a desuden indført mellem anlægget 10 og indsnævringen 4 i det konvergent- divergente stykke 3.In order that the lime can be distributed in a completely homogeneous manner in the reaction column, a spreader 10a is also inserted between the plant 10 and the constriction 4 in the convergent divergent piece 3.

10 Afgangen fra reaktionskolonnen 1 er forbundet med en cyklon 13, hvis gasafgang 14 er forbundet via et rør 15 med en støvudskiller 16, f.eks. et elektrofilter, og udførslen for udskilt materiale fra cyklonen 13, betegnet 17, forsyner en tragt 18, forbundet via en anden doseringssnegl 19 med den 15 førnævnte tilbageføringsledning 12.The exit from the reaction column 1 is connected to a cyclone 13, the gas outlet 14 of which is connected via a pipe 15 to a dust separator 16, e.g. an electrofilter, and the discharge of excreted material from the cyclone 13, designated 17, provides a hopper 18 connected via a second metering screw 19 to the aforementioned return line 12.

Via en tragt 20, der forsynes fra cyklonen og en doseringsventil 21, kan en forudbestemt del af asken og materialet, anvendt til behandlingen og skilt fra røggasserne, udtages via 20 ledninger 22 og 23 og derefter oplagres i en silo 24. Blandingen af sulfat og aske tilført til denne silo, kan med givne tidsintervaller bortskaffes ved hjælp af et transportmiddel 25.Via a hopper 20 supplied from the cyclone and a metering valve 21, a predetermined portion of the ash and material used for the treatment and separation of the flue gases can be extracted via 20 lines 22 and 23 and then stored in a silo 24. The mixture of sulfate and ash supplied to this silo can be disposed of at a given time interval by means of a transport means 25.

25 Gasafgangen 26 fra elektrofi 1 tret 16 er forbundet via en blæser 27 med en skorsten 28 til en udledning af de behandlede røggasser. Det fine støv, der samler sig i elektrofi 1 terets tragt 29, kan ligeledes transporteres til bortskaffelsessiloen 24 via en doseringsventil 30 og en ledning 31, forbundet til 30 de nævnte ledninger 22-23. Ledningerne 22-23 og 31 kan hensigtsmæssigt være af typen med pneumatisk transport.The gas outlet 26 from the electrophoresis 16 is connected via a blower 27 to a chimney 28 to discharge the treated flue gases. The fine dust that accumulates in the funnel 29 of the electrofitter 1 can also be conveyed to the disposal silo 24 via a metering valve 30 and a conduit 31, connected to said conduits 22-23. Conduits 22-23 and 31 may conveniently be of the pneumatic conveying type.

Det skal bemærkes, at mængden af vand, som i anlægget 10 tilføres kalken, dvs. blandingen af tilført kalk og kalk tilbage-35 ført med aske, er relativ ubetydelig, (10 vægt% af det tørre materiale), hvilket i øvrigt takket være de førnævnte spredere 10a muliggør indførsel af et materiale til anvendelse ved be-It should be noted that the amount of water supplied in the system 10 to the lime, i.e. the mixture of added lime and lime returned with ash is relatively negligible (10% by weight of the dry material), which, moreover, thanks to the aforementioned spreaders 10a, allows the introduction of a material for use in

Claims

A method for semi-dry removal of pollutants, especially sulfur dioxide, contained in flue gases, by treatment with a basic powdery lime type material, in which the flue gases in an upward flow of the flue gases in a reaction and drying column are brought into intimate contact with the material so that the latter, by chemical reaction, absorbs the pollutants, especially acids contained in the flue gases, after which a separation of the treated gas and the material used for the treatment is carried out, and then the purified gases can be discharged into the atmosphere, characterized in that the dry powdery material is added to an amount of water of approx. 10% by weight of the dry material immediately before it is introduced into the reaction and drying column.

Process according to claim 1, characterized in that the material used for the treatment is a mixture of fresh powdered, basic material and recycled material, ie. material that has already been used for the treatment.

Process according to claim 2, characterized in that at flue gases having a temperature of approx. 150 ° C and a sulfur dioxide content of approx. 4000 ppm as material for the treatment uses applied lime in an amount of approx. 10-20 g / Nm3 flue gas in admixture with recycled lime and ash in an amount of approx. 80 g / Nm3 of flue gas, the amount of water thus supplied being approx. 10 g / Nm3 flue gas. 5 10 15 20 25 30 35